World of Physical Science

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CHAPTER 1

• World of Physical Science

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Section II The Scientific
Method Though the scientific method has several
steps, real scientists may take the steps in
different order, skip steps or repeat steps in
order to try to find the answer to a question.
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Ask a question (Step 1) 1. Questions are usually
asked after scientists have made a lot of
observations.
a. Observations are any use of the senses to
gather information. (Sometimes this is called
Qualitative data)
b. Measurements are observations made with
instruments. (Sometimes this is called
Quantitative data)
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From a Hypothesis (Step 2) 1. A Hypothesis is a
possible explanation or answer to a question.
a. Scientists generally form hypotheses that can
be tested. Where observations and can be made and
information can be gathered.
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Hypothesis that cannot be tested are neither
right or wrong because there is no way to support
or not support them. ( these hypothesis exist but
are neither right or wrong but are not considered
valid, because to be valid, they must be
testable and supported by evidence that means
proven right!)
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Test the hypothesis (Step 3) 1. After a
hypothesis is formed, you must test it to
determine if it is a reasonable answer to your
question.
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2. One way to test a hypothesis is a controlled
experiment.

• A controlled experiment has
• Independent variable- the part of the experiment
  you manipulate.
• Dependant variable the part of the experiment
  that changed because of what you changed.
• Controlled factors- What other things in the
  experiment must be held the same so that it does
  not mess up the results.

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Analyze the results (Step 4) 1. All of the
collected data needs to be studied to see if the
test supports the hypothesis.
2. Putting information into tables and graphs
helps to make the relationships between the
information easier to see.
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Draw conclusions (Step 5) 1. After looking at
the data you must decide if the information
supports your hypothesis or not.
a. If it does support the hypothesis you can ask
further questions.
b. If it does not support the hypothesis you can
check you results for errors or modify your
hypothesis.
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Communicate results (Step 6) 1. Most scientist
publish their results in magazines and academic
papers.
2. Most students publish results in a lab paper.
REMEMBER-NOT all scientists use the
scientific method.
Scientific Method Video Courtesy
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DEVELOP A MEMORY TRICK

• A
• H
• T
• A
• C
• C

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Lab design
Imagine you are conducting an experiment in which
you are testing the effects of the height of the
ramp on the speed at which a toy car goes down
the ramp.
Hypothesis - what is the relationship you are
trying to discover? Independent variable- the
part of the experiment you manipulate. Dependant
variable the part of the experiment that
changed because of what you changed. Controlled
factors- What other things in the experiment
must be held the same so that it does not mess
up the results.
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Lab design

• A doctor has developed a new headache medicine.
  How should he set up his test trials to figure
  out if it works?
• Hypothesis
• Independent variable
• Dependant variable
• Controlled factors

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Lab design
Med 1 Med 2 Med 3 No med
People with headaches out of 100 5 20 30 20
What to the results tell you about the different
medicines?
Why is a group with no medicine included?
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Building scientific knowledge. 1. Answers in
sciences are rarely final answers. As our
understanding grows our ideas about the world
around us changes.
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2. A Scientific Theory is a unifying explanation
for a broad range of hypothesis and observations
that have been supported by testing (Often
explains why). It can be changed as new
observations are made and new hypothesis are
tested.
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3. A Scientific Law is a summary of many
experiments and observations. They tell you how
things work. They only explain what happens, not
why.
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• What is the difference between a theory and a
  law?
• A theory is based on supported hypothesis's where
  as a law is based on the results of the
  experiment instead of the hypothesis
• A _____ is a summary of many different
  experimental results and observations
• Law

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III. USING MODELS IN SCIENCE (p.20-23) A. What
is a model?
1. A model is a representation of an object or
system. Including scientific ideas and objects
2. They can be used to make predictions or
explain observations.
3. Models are never exactly like the object or
system. 4.They can be tools used to conduct an
investigation 5.They can illustrate theories In
what other ways might models be helpful?
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IV. MEASUREMENT AND SAFETY IN SCIENCE
(p.24-27) A. The International System of Units
1. It helps scientists compare their information.
2. All units are based on the number 10.
SI Video Courtesy http//www5.unitedstreaming.com
/index.cfm
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3. Length The Meter is the basic unit of
length. Other SI units of length are larger or
smaller than meters by multiples of 10. The tool
used to measure length is a meter stick or ruler
1. 10 meters is equal to how many cm? 1000cm
How many mm? 10,000mm 2. 500 meters is
equal to how many km? 0.5 km 3. 500 cm is equal
to how many meters? 5 meters How many mm?
5000mm How many km? 0.005 km
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4. Volume- the amount of space that something
occupies. The tool used to measure volume is a
graduated cylinder
a. Volume of liquids is expressed in Liters (L).
b. Liters are based on the meter, 1000 liters
will fit into a cubic meter.
c. A milliliter (ml) will fit in to a box one
centimeter (cm) on a side.
1. How many ml in one cm3 ?
one
2. How many ml in a liter?
1000
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d. Volumes of solid objects are expressed in
cubic meters (m3) smaller objects are expressed
in cm3 or mm3.
e. To find the volume of a rectangular shape,
multiply length x width x height.
f. To find the volume of an irregularly shaped
object, measure how much liquid it displaces.
What is the label or unit for the volume of a
rock?
cm 3 because it is a solid
What is the label for a volume of gasoline?
ml because it is a liquid
What is the volume of a box that is 3 cm long, 10
cm tall and 3 cm wide?
3 x10 x3 90cm3
There is 30 ml of water in a graduated cylinder.
After a rock is placed in the cylinder the water
level measures 45ml. What is the volume of the
rock?
15 cm3
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5. Mass- the amount of matter something is made
of. The kilogram is the basic unit of mass. Grams
are used to measure smaller objects. 1000 kg is a
metric ton. The tool used to Measure mass is A
balance.
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6. Temperature- how hot or cold something is.
Scientist usually uses the Celsius scale (Co) to
measure temperature. Kelvin is the SI unit of
temperature. Fahrenheit is the most common unit
of temperature in the United States.
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B. Derived Quantities- formed from a combination
of other measurements. 1. Area- a measure of how
much surface an object has. It is determined by
multiplying length times width.
2. Density- is mass per unit volume D m/v
1. A cereal box has the dimensions of 27 cm x19cm
x 6 cm. What is the area of the front of the box.
( Hint how can you tell which numbers to use?)
27cm x 19 cm 513cm2
2. What is the volume of the box?
27cm x 19 cm x 6 cm 3078 cm3
3. If the box has a mass of 340 g what is the
density of the box?
340g / 3078 cm3 0.110g/cm3 ( three significant
figures)
(Demonstrate triangle equation)
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C. Safety rules- 1. Pre read labs and read the
safety information on p.622.
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